By Erwin chargaff
It states that in all DNA, Pyrimidines and Purines must have 1:1
Adenine : Thymine
Cytosine : Guanine
i.e., the amount of adenine = amount of thymine
similarly, the amount of cytosine = amount of guanine.
It indicated that DNA is symmetrical. (A) Double bond (T) and (C) triple bond (G)